GUNNARSHOLT, Iceland — With his flats of saplings and a red planting tool, Jon Asgeir Jonsson is a foot soldier in the fight to reforest Iceland, working to bring new life to largely barren landscapes.

The country lost most of its trees more than a thousand years ago, when Viking settlers took their axes to the forests that covered one-quarter of the countryside. Now Icelanders would like to get some of those forests back, to improve and stabilize the country’s harsh soils, help agriculture and fight climate change.

But restoring even a portion of Iceland’s once-vast forests is a slow and seemingly endless task. Despite the planting of three million or more trees in recent years, the amount of land that is covered in forest — estimated at about 1 percent at the turn of the 20th century, when reforestation was made a priority — has barely increased.

“It’s definitely a struggle,” said Mr. Jonsson, a forester who works for the private Icelandic Forestry Association and plants saplings with volunteers from the many local forestry groups in this island nation of 350,000 people. “We have gained maybe half a percent in the last century.”

Even in a small country like Iceland, a few million trees a year is just a drop in the bucket.

Iceland’s austere, largely treeless landscapes, punctuated by vast glaciers and stark volcanoes, have long been a favorite of the film industry.

The picturesque vistas also have helped fuel a tourism boom. Nearly 1.8 million foreigners visited the country last year.

But with that beauty comes a problem that Icelanders have faced for centuries. The lack of trees, coupled with the ash and larger pieces of volcanic rock spewed by eruptions, has led to severe soil erosion.

With vegetation unable to gain much of a foothold, farming and grazing have been next to impossible in many parts of the country. And the loose soil, combined with Iceland’s strong winds, has led to sandstorms that can further damage the land — and even blast the paint off cars…